Internal combustion engines typically have a main body forming cylinders and a cylinder head for closing one end of cylinders. The cylinders, pistons reciprocating in the cylinders, and the cylinder head define a combustion chamber having a variable volume therebetween. A valve is arranged in the internal combustion engine, to provide one of a flow of air and a mixture of air and fuel into the combustion chamber. Typically a separate valve is arranged in the cylinder head to provide exhausting of exhaust gases from the combustion chamber.
In most internal combustion engines poppet valves are used to control the inflow and outflow of gases into the combustion chamber. These poppet valves are typically activated by a camshaft, which is rotatably coupled by a drive element to a crankshaft of the internal combustion engine. The rotatable coupling of the crankshaft to the camshaft provides a constant ratio between the speed of rotation of the crankshaft and the speed of rotation of the camshaft. The activation of the individual valves is thus fixed to the rotation of the crankshaft. Sometimes no independent control of the valves is possible even if it is desired to achieve improved engine performance and/or emission characteristics.
The poppet valves are typically spring biased to a closed position thereof. To open the valve, the camshaft has to first overcome the bias of the springs, which leads to large energy expenditure for opening of the valves.
An alternative internal combustion engine using spherical rotary intake and outlet valves in a cylinder head is shown in U.S. Pat. No. 6,779,504, issued to Coates on Aug. 24, 2004. The Coates cylinder head is formed by two separate body portions. The body portions when assembled to each other define a plurality of spherical valve chambers each conformed to the shape of a single spherical valve to be accommodated therein. The spherical rotary valves are mounted to a drive shaft, which is rotatably coupled to the crankshaft of the internal combustion engine. The rotatable coupling of the crankshaft to the camshaft again provides a constant ratio between the speed of rotation of the crankshaft and the speed of rotation of the camshaft. Again no flexibility is provided for changing the timing of valve opening and closing events with respect to the crankshaft position.
Flow of air between the cylinder head and the cylinder is controlled by each of the spherical rotary valves accommodated in the cylinder head. In particular, flow of gases is allowed through an opening in the spherical surface of the rotary valve, which is brought into alignment with a flow opening in the lower body part of the cylinder head, and through the side surfaces of the spherical rotary valves.
At the beginning of a valve opening event, the flow through the rotary valve increases gradually. Similarly, at the end of an opening event, the flow through the rotary valve decreases gradually. A fast opening and closing would, however, be desired to optimize the flow of gases through the rotary valves.
The present application is directed to overcoming one or more of the problems set forth above.